Space discharge device



Sept. 1, 1931. A. w. HULL. 1,821,808

' SPACE DISCHARGE DEVICE l Filed Aug. 51', 1927 fgl.

Inventor z Albevt W. HUH,

His Attorney.

Patented Sept. v1i, 1931 UNITED STATESl PATENT oFF-ICE 'ALBERT W. HULL, 0F SOHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF -NEW YORK lSI'AQE DISCHARGE DEVICE Application mea august s1, 1927. 'serial No. 216,679.

The present invention relates to space discharge devices and more particularly to an arrangement for controlling a three-electrode space discharge device by means of light impulses.

It is one of the objects of the present invention to provide an improved three-electrode space discharge device in which no leadingin wire is brought through the glass container from the control member of the discharge device.

The Anovel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, will best be understood from reference to the following specification when considered in connection with the` accompanying drawings in which Fig. 1 represents a viewv partly broken away of a three-element space 4discharge device which embodies the features of my invention; Fig. 2 shows diagrammatically one application of' the discharge device shown in Fig. 1, while Figs. 3 and 4 show modified forms of the invention disclosed in Fig. 1.

Referring more particularly to the drawtrodes 2O and 21 which cooperate with a light sensitive, cylindrical electrode 22. Electrode 22 is connected to the leading-in Wire 13. Electrodes 20 and 21 are supported by a pair of insulating beads 23 land 24 of refractory material, such as quartz, alumina or other suitable substance of high insulating quality.v These beads are mounted on the ends of short wire stems 25 and 26 which are fused into the end of the glass stem 12.

A light sensitive coating is obtained on the electrode 22, as well as on the electrode 19, by vaporizing a small amount of caesium or other alkali metal within the container 10,

The plate member 19- or by suitably treating the respective surfaces.

With the construction indicated it will be apparent that the potential of the plate electrode 19 is controlled by the electrodes 20 and 21 which are electrically insulated from the exterior of the receptacle 10, and that no lead 'for the control electrode 19 extends through the stem 12. In this manner any electrical leakage along the surface of the glass stem or reentrant portion 1l is prevented. l

Although beads of quartz or alumina, such as 23 and 24, provide excellent electrical insulation under ordinary vacuum conditions, it may be found advisable when employing an excess of free caesium in the tube, -to surround the beads with coils 27 and 28 which are included in the filament circuit, as indicated in Fig. 3. The heat produced by the current flowing through these coils heats the beads sufficiently to prevent any condensation of caesium onto the beads thereby to preclude electrical leakage. Or if desired cupshaped shields 28 may be mounted over the insulating beads as indicated in Fig. 1.

In the arrangements shown in Fig. 4 the upperpart29 ofthe envelope or container comprises a light sensitive ce'll which is separated from the lower three-element discharge device o-r valve 30 by a glass partition 31. In this ligure the control electrode of the 'threeelement discharge device is the usual grid 18 and it is connected to the cathode element' 32 of' the light sensitive cell 29 by wires 33 and 34, while the anode member 19 of the discharge .device is connected to the electrode 35. Operation of this fornnof discharge device is similar to the operation of the devices shown in Figs. 1 and 3. The separation of the container into two parts, however, permits the application of light sensitive material solely to the elements comprising the light sensitive or photo-electric cell. The filament of the amplifier may therefore be of any tvpe, for example a thorium. coated tungsten filament, without danger of excess photo-electric action of its light upon the grid.

One application of mv improved discharge device is indicated in Fig. 2 which discloses diagrammatically a circuit arrangement for automatically controlling the temperature of an electric furnace by means of light given oil by the furnace. shown the filament 17 is supplied from a suitable source of energy 36 through a ballast lamp 37 which serves to keep the temperature of the filament substantially constant. Light from a furnace to be controlled is directed on to the light sensitive cylindrical electrode 22 through an opening 38 therein, causing this electrode to give up electrons to the wiresA or electrodes 2O and 21 which are connected to the plate or control electrode 19. This action tends to make the plate 19 less positive. At the same time, however, light from the ilamentary electrode 17 falls upon the control member 19, which is coated with csium and causes it to lose electrons and become more positive and thereby normally establishing a balanced photo-electric effect between the light from the filament 17 and the light directed onto the electrode 22. If the light from the furnace is weak the plate or control electrode 19 will obviouslv be positive and current will fiow in the anode or output circuit of. thedischarge device. A resistor 39 is included in the output circuit of the discharge device and the drop across this resistor will control the potential supplied to the grid or control element 40 of a second discharge device 41. 'When the full output current of the first discharge device is flowing the potential applied to the grid 40 will be so negative that the discharge device 41 will not operate. No current f'lows in its output circuit under such circumstances and relayr '42 included in the output circuit of tube 41 remains deenergized. If the temperature of the furnace to be controlled is raised slightlv so that the light from it exceeds a predetermined amount,y the control elect-rode 19 will become negative thus cutting off the fiow of' anode current.allowingthe grids 40 of they discharge device 41 to assume cathode potential, and permitting current to flow in the outnut circuit of tube 41` therebv energizing relav 42 and in that manner adjusting the resistance of the furnace.

In the arrangement shown in Fig. 4 it will be apparent that when the filament i s lighted, electrons are supplied to the grid tending to make it negative and that light supplied to the cylindrical electrode removes electrons from the grid thereby tending to make it positive and in thismannerestablishingabalanced effect between the light from the filament and light directed onto the light sensitive cell.

In the arrangement What I claim as new and desire to secure by Letters Patent of the United States,is

1. In combination, a photo-electric device comprising a receptacle having a reentrant portion provided with a stem, alcathode, anode and control electrode, mounted in said device, said control electrode being coated with a highly reactive light-sensitive material, leading-1n wires extending through said reentrant portion and stem and connected to the anode and cathode and means for sup ,porting thel control electrode on said stem said means comprising an insulating bead of refractory material and means for preventing the collection of excess light-senstive material on said bead.

2. A space discharge device comprising an anode, a ilamentary electrode and a control electrode, said control electrode being provided with a light sensitive surface, means for normally balancing the photo-electric efi'ect produced by the action of the lighted filament on said control electrode, said4 means comprising another light sensitive electrode, and a second electrode cooperating with said light sensitive electrode and connected to the control electrode.

3. A space discharge device comprising an anode, a filamentary electrode and a control electrode, said control electrode being provided with a light sensitive surface, means for normally balancing the photo-electric 'effect produced by the action of the lighted filament on said control electrode, said means comprising another light sensitive electrode and a second electrode cooperating with said light sensitive electrode and connected to the control electrode but insulated from the outside of said discharge device.

4. In combination, a photo-electric device comprising a receptacle having a reentrant portion provided with a stem, a cathode, anode and control electrode mounted in said device, said control electrode being coated with a highly reactive light-sensitive material, leading-in Wires extending through said stem and connected to the anode and cathode,

means for supporting the control electrode y on said stem and means f orpreventing electrical leakage about the supporting means.

In witness whereof I have hereunto set my hand this 29th day of August, 1927.

ALBERT W. HULL.

The action in the device shown in this figure is similar to the action which takes place in the device shown in Figs. 1 and 3, but the a1'- rangement disclosed in Fig. 4 requires one less .leading-in wire than the devices shown in Figs. 1 and 3 and avoids the use of alumina or quartz insulating beads. 

